arm64: Hyper-V: fixing hung issue during Hyper-V initialization

In non-Hyper-V systems during Hyper-V initialization, system
initialization was getting hung, as hyperv_identify(),
was returning successful irrespective of the type of the platform.

Reviewed by: andrew, whu
Fixes: 9729f076e4d
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D37219